The Pratt & Whitney Hornet series occupies a significant place in the development of reliable and powerful engines for both commercial and military operators. The series began with the 1926 development of the air-cooled R-1690 for the U.S. military, and was Pratt & Whitney’s second major engine, following the Wasp, another 1926 development. This early version of the Hornet allowed the first practical torpedo plane, the Martin T4M which carried a 909 kg (2000 lb) torpedo for a range of 1079 km (665 miles).
First certificated in 1929, the R-1860-B was a larger version for use in civil and military aircraft in the United States and abroad. Pratt & Whitney manufactured this particular R-1860-B Hornet for the U.S. Army Air Corps in 1932. The engine is most closely associated with the Sikorsky S-40 and S-41B flying boats. Subsequently, Pratt & Whitney engines powered nearly every flying boat built by Sikorsky.